Brittle bone disease

Osteogenesis imperfecta (OI), commonly known as brittle bone disease, is a group of genetic bone disorders. People with OI either have less collagen than normal or the quality is poorer than normal. As collagen is an important protein in bone structure this impairment causes those with the condition to have weak or fragile bones. more...

As a genetic disorder, OI is a autosomal dominant defect. Most people with OI receive it from a parent but it can also be an individual (de novo or "sporadic") mutation.

Types

There are four types of OI, though the symptoms range from person to person. Type I is the most common and mildest form, followed by Type IV, Type III and Type II. A Type V has been proposed based on studies of Type IV.

Type I

• OMIM 166200 - Type I
• OMIM 166240 - Type IA

Collagen is normal but not of a high enough quantity:

• Bones fracture easily, especially before puberty
• Slight spinal curvature
• Loose joints
• Poor muscle tone
• Discolouration of the sclera (whites of the eyes)
• Early loss of hearing

Type II

• OMIM 166210 - Type II

Collagen is not of a sufficient quality or quantity

• Most cases die before adulthood
• Severe respiratory problems due to underdeveloped lungs
• Severe bone deformity and small stature

Type III

• OMIM 259420 - Type III

Collagen quantity is sufficient but is not of a high enough quality

• Bones fracture easily, sometimes even before birth
• Bone deformity, often severe
• Respiratory problems possible
• Short stature, spinal curvature and barrel-shaped rib cage
• Loose joints
• Poor muscle tone in arms and legs
• Discolouration of the sclera (whites of the eyes)
• Early loss of hearing

Type IV

• OMIM 166220 - Type IV

Collagen quantity is sufficient but is not of a high enough quality

• Bones fracture easily, especially before puberty
• Short stature, spinal curvature and barrel-shaped rib cage
• Bone deformity is mild to moderate
• Discolouration of the sclera (whites of the eyes)
• Early loss of hearing

Treatment

At present there is no cure for OI so treatment is aimed at maintaining mobility and strengthening bones as much as possible.

Physiotherapy is used to strengthen muscles and improve motility in a gentle manner which minimises bone breakages. This often involves hydrotherapy and the use of support cushions to improve posture. Individuals are encouraged to change positions regularly throughout the day in order to balance the muscles which are being used and the bones which are under pressure. One of the biggest problems is that children often develop a fear of trying new ways of moving due to movement being associated with pain. This can make physiotherapy difficult to administer to young children.

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